[Keyboard] Add spankbd, 3x5+3 split keyboard (#22003)

keyboards/idank/spankbd/readme.md

@@ -0,0 +1,28 @@
+# Span
+
+*Span is a 3x5+3 split keyboard, with 2u, 1.5u, 1u thumb clusters.*
+
+The keyboard layout Span uses is derived from GergoPlex, a keyboard that was originally available on gboards.ca
+(now defunct).
+
+* Keyboard Maintainer: [@idank](https://github.com/idank)
+* Hardware Supported: [spankbd](https://github.com/idank/spankbd)
+* Hardware Availability: *[holykeebs](https://holykeebs.com)*
+
+Make example for this keyboard (after setting up your build environment):
+
+    make idank/spankbd:default
+
+Flashing example for this keyboard:
+
+    make idank/spankbd:default:flash
+
+See the [build environment setup](https://docs.qmk.fm/#/getting_started_build_tools) and the [make instructions](https://docs.qmk.fm/#/getting_started_make_guide) for more information. Brand new to QMK? Start with our [Complete Newbs Guide](https://docs.qmk.fm/#/newbs).
+
+## Bootloader
+
+Enter the bootloader in 3 ways:
+
+* **Bootmagic reset**: Hold down the key at (0,0) in the matrix (usually the top left key or Escape) and plug in the keyboard.
+* **Physical reset button**: Briefly press the button on the front of the PCB. Double tap for pro micro, 1 second press for Sea Picro / RP2040s.
+* **Keycode in layout**: Press the key mapped to `QK_BOOT` if it is available.